The present invention relates generally to fluxing apparatus and methods, and more particularly to fluxing apparatus and methods that are adapted to dispense and apply water soluble soldering flux.
Conventional flux application apparatus for use in liquid wave soldering systems, for example, employs a flux bath that uses a stone having a plurality of perforations therein that is immersed in the flux. A chimney arrangement is disposed above the stone and air is forced through the stone. The forced air creates flux foam that bubbles up through the chimney to a point slightly above the top of the chimney.
A conveyor carries a circuit card assembly that is to be soldered along a path whereupon the flux bubbles coat the bottom surface of the circuit card assembly as the conveyor moves it over the chimney. The flux-coated circuit card assembly then passes through a pre-heater that elevates the temperature of the card and evaporates excess flux solvent from the bottom of the card. The circuit card assembly then is moved over a solder wave whereupon the circuit card assembly is soldered.
This conventional fluxing technique employs fluxing materials that must be cleaned and degreased by using highly toxic chemicals and hence creates an environmental disposal problem for the remnants of the chemicals employed. Most fluxes and defluxing chemicals used in the soldering industry contribute to ozone depletion of the atmosphere or are considered to be environmental pollutants or health hazards. Certain chloroflurohydrocarbons used in vapor degreasing operations to clean soldered parts that were soldered with rosin-based fluxes, and alcohols, and the like pose health risks and disposal problems for the industry.
However, a recent advance in soldering fluxes has been achieved which is disclosed in U.S. patent application Ser. No. 523,765, filed on May 15, 1990, entitled "Water-Soluble Soldering Flux," and assigned to the assignee of the present invention. The contents of this application are incorporated herein by reference in its entirety. This water soluble flux is generally comprised of a water soluble organic acid, such as citric acid, and a non-toxic carrier such as water. The flux eliminates harmful environmental emissions normally associated with rosin-based fluxes, flux thinner, and defluxing solvents.
It is believed, that heretofore, solder flux, and in particular water soluable solder flux, has not been sprayed or misted onto surfaces of solderable components. Accordingly, it is an objective of the present invention to provide for fluxing apparatus and methods that are adapted to apply water soluble flux to circuit card assemblies, and the like.